I was not sure what to do so I thought of something really simple to start with. If you ever need to make buttons here is a cheap easy way to do it. I have done it this way for all my figures so far. I think this would help even if you are going to just convert a plastic figure.

Ok, here is the way I go about it.

I have always wanted to use a punch and die but just never got around to buying one. I use the back end of a drill bit placed inside of a holder. I then press it into sheet lead. In this example I wanted nice flat round buttons, so I used the wooden base. I have also used this same method but punched it into a cutting mat and this gave me a dome shape.